The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE-A) architecture, are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as video streaming and video conferencing on mobile communications devices that would previously only have been available via a fixed line data connection.
The anticipated widespread deployment of third and fourth generation networks has led to the parallel development of a class of devices and applications which, rather than taking advantage of the high data rates available, instead take advantage of the robust radio interface and increasing ubiquity of the coverage area. Examples include so-called machine type communication (MTC) applications, some of which are in some respects typified by semi-autonomous or autonomous wireless communication devices (MTC devices) communicating small amounts of data on a relatively infrequent basis. Examples include so-called smart meters which, for example, are located in a customers home and periodically transmit data back to a central MTC server relating to the customers consumption of a utility such as gas, water, electricity and so on. Smart metering is merely one example of potential MTC device applications. Further information on characteristics of MTC-type devices can be found, for example, in the corresponding standards, such as 3GPP TS 22.368 version 13.1.0 Release 13 (2014-12) [1].
Whilst it can be convenient for a terminal such as an MTC-type terminal to take advantage of the wide coverage area provided by a third or fourth generation mobile telecommunication network there are at present disadvantages. Unlike a conventional third or fourth generation mobile terminal such as a smartphone, a primary driver for MTC-type terminals will be a desire for such terminals to be relatively simple and inexpensive. The type of functions typically performed by an MTC-type terminal (e.g. simple collection and reporting/reception of relatively small amounts of data) do not require particularly complex processing to perform, for example, compared to a smartphone supporting video streaming. However, third and fourth generation mobile telecommunication networks typically employ advanced data modulation techniques and support wide bandwidth usage on the radio interface which can require more complex and expensive radio transceivers and decoders to implement. It is usually justified to include such complex elements in a smartphone as a smartphone will typically require a powerful processor to perform typical smartphone type functions. However, as indicated above, there is now a desire to use relatively inexpensive and less complex devices which are nonetheless able to communicate using LTE-type networks.
Amongst the techniques proposed to reduce the complexity, cost and power consumption of such devices, a first one is the restriction of the frequency band that the devices operate on. Currently, it has been proposed that a Low Complexity (“LC”) terminal would operate in a bandwidth of no more than 6 Physical Resource Blocks “PRBs”. In LTE, 6 PRBs correspond to bandwidth of 1.4 MHz. When a limited bandwidth is provided for a terminal with limited capabilities to operate on is provided, it is often referred to as a “narrowband”. The bandwidth of the telecommunication system can therefore be divided into multiple 6 PRBs narrowbands and an LC-MTC terminal is expected to be able to tune into any of these narrowbands.
Another technique to increase coverage for MTC and LC-MTC devices is the use of repetitions. In this Coverage Enhancement (CE) feature, the coverage for LC-MTC can be extended by up to 15 dB (relative to that of Cat-1 terminal) by repeating the symbols or messages transmitted to the LC-MTC. Using numerous repetitions of the same information, the coverage provided by the base station can be extended.
While the narrowband technique enables a simplification of the terminal by reducing the operative bandwidth, thereby reducing costs, complexity and power consumption, integrating narrowband terminals in a legacy system that has been conceived and designed with full-bandwidth terminals in mind can be challenging and it can prove difficult for a LC terminal to operate normally when it is not able to receive signals across the entire bandwidth of the system.